Book excerpt: From Charles Atlas to Jane Fonda, the fitness movement has been a driving force in American culture for more than half a century. What started as a means of Cold War preparedness now sees 45 million Americans spend more than $20 billion a year on gym memberships, running shoes, and other fitness-related products. In this first book on the modern history of exercise in America, Shelly McKenzie chronicles the governmental, scientific, commercial, and cultural forces that united-sometimes unintentionally--to make exercise an all-American habit. She tracks the development of a new industry that gentrified exercise and made the pursuit of fitness the hallmark of a middle-class lifestyle. Along the way she scrutinizes a number of widely held beliefs about Americans and their exercise routines, such as the link between diet and exercise and the importance of workplace fitness programs. While Americans have always been keen on cultivating health and fitness, before the 1950s people who were preoccupied with their health or physique were often suspected of being homosexual or simply odd. As McKenzie reveals, it took a national panic about children's health to galvanize the populace and launch President Eisenhower's Council on Youth Fitness. She traces this newborn era through TV trailblazer Jack La Lanne's popularization of fitness in the '60s, the jogging craze of the '70s, and the transformation of the fitness movement in the '80s, when the emphasis shifted from the individual act of running to the shared health-club experience. She also considers the new popularity of yoga and Pilates, reflecting today's emphasis on leanness and flexibility in body image. In providing the first real cultural history of the fitness movement, McKenzie goes beyond simply recounting exercise trends to reveal what these choices say about the people who embrace them. Her examination also encompasses battles over food politics, nutrition problems like our current obesity epidemic, and people left behind by the fitness movement because they are too poor to afford gym memberships or basic equipment. In a country where most of us claim to be regular exercisers, McKenzie's study challenges us to look at why we exercise-or at least why we think we should-and shows how fitness has become a vitally important part of our American identity.